The present invention relates to a method and an apparatus for the shaping of plastics material pre-forms into plastics material containers. Apparatus of this type have long been known from the prior art.
In recent years it has also become known in this case for blow moulding machines of this type, and also in particular stretch blow moulding machines, to be provided with air recycling systems. In this case it is possible for plastics material pre-forms to be acted upon with different pressure levels for the expansion thereof, and in this way compressed air can possibly be recovered again. A presently current machine of the Applicants has in this case two pressure ducts which are capable of being recycled. These are a pressure duct which provides available a preliminary blow moulding pressure and a pressure duct which provides an intermediate blow moulding pressure. In particular, the level of the so-called intermediate blow moulding significantly influences the air consumption, in which case, however, an ideal air consumption can be predicted only with difficulty.
DE 10 2004 041 973 B3 describes an air recycling in a blow moulding process. In this case an aeration of the container with respect to an environmental pressure is carried out after a transition phase and a pressure control in the lower compressed air supply is carried out by a variation in the duration of this transition phase.
It has been found, however, that with this method the full potential of a possible saving cannot yet be exploited.
The object of the present invention is therefore to improve the pressure consumption for blow moulding machines of this type still further.